1. Field of the Invention
The invention relates to a take-up unit for taking up a synthetic filament yarn onto a cop of the type which has a rotary drive which carries the cop and which causes the cop to rotate at a speed which can be set, with a balloon thread guide which is located in the axial direction at a considerable distance from the cop, with a ring holder which surrounds the cop at a constant radial distance with the race located therein and a ring traveler which runs on the race, with a ring holder drive which carries the ring holder and which moves the ring holder back and forth parallel to the longitudinal axis of the cop between the ends of the cop, take-up of the filament yarn onto the cop taking place according to predetermined cop generation factors and such that the cop, at the conclusion of take-up, has a roughly cylindrical middle area of large diameter and end areas of diameters which decrease towards the end of the cop except for the raw diameter of the cop.
2. Description of related Art
Take-up units of the type under consideration are generally parts of ring spinning frames or ring doubling frames. As the thread carrier, the cop has a smooth, slender sleeve of small diameter and is wound with the filament yarn with turns which are essentially parallel, in contrast to cross-wound bobbins which are wound with crossing turns. A cop wound with synthetic filament yarn has a roughly cylindrical middle area of large diameter, and on the ends which adjoin areas on which the yarn has been wound on, the diameter decreases towards the end of the cop as far as the raw diameter of the thread carrier.
The synthetic yarn is delivered by a pretreatment section of the take-up unit system with a certain delivery speed of, for example, 1000 to 1200 m/min. The cop rotates with a speed which can be changed by the control, but which is essentially constant, for example, a speed of roughly 11000 rpm. This corresponds in the not yet wound thread carrier of the cop to a certain peripheral speed of, for example, 1700 rpm. The difference of the speeds is accommodated by a ring traveler which is entrained by the filament yarn wound onto the cop. This ring traveler rotates on a race of the ring holder which surrounds the cop with a constant radial spacing. In this example, the ring traveler would have a peripheral speed of roughly 700 rpm, according to the difference of the peripheral speed of the thread carrier and the delivery speed of the filament yarn. Due to the much greater diameter of the track of the ring traveler relative to the outside surface of the thread carrier of the cop the ring traveler in a sample case has a speed of only roughly 1500 rpm.
As explained above, the ring traveler is entrained by the filament yarn wound onto the cop; factors oppose this entrainment which try to brake the ring traveler on the race. For example, there is the friction of the ring traveler on the race, and also there is the air resistance of the filament yarn between the balloon thread guide and the ring traveler which is especially high. The filament yarn in this area also rotates with the speed of the ring traveler, inflates into a so-called "balloon", and of course, it has considerable air resistance.
It is apparent from the above explanation that the difference of speed between the thread carrier of the cop, on the one hand, and the ring traveler, on the other, determines the take-up speed for the filament yarn on the thread carrier of the cop. The motion of the ring traveler on determines the circumference in which the filament yarn is twisted. If there were no difference of speed, the filament yarn would only be twisted, but not taken up, and the ring traveler would not move, the delivery speed for the filament yarn, aside from stretching, would have to be equal to the take-up speed of the cop. Between these two extremes is the working range of the take-up unit.
Several take-up units of the type under consideration are often combined into a so-called ring rail (published German Patent Application DE-A-196 07 790). The invention proceeds from this prior art.
The ratio of the rpm and peripheral speed of the cop depends on the diameter present at the time. With increasing take-up of the filament yarn, in the cylindrical middle area, there is an increasing diameter, while in the end areas, the slope of the winding-on becomes greater and greater. If an unchanged rpm of the cop is assumed, a greater diameter of the wound yarn means that the periphral speed increases. However, since the delivery speed of the filament yarn from the pretreatment section does not increase, the speed of the ring traveler must increase accordingly.
The ring traveler is moved back and forth by the ring holder drive between the ends of the cop in order to wind onto the cop uniformly. In the end areas, where the diameter of the wound-on yarn decreases toward the ends of the cop, the peripheral speed of the cop decreases dramatically towards the ends, just because the diameter decreases towards the ends. The traveler speed first the same, in any case follows the decrease of the peripheral speed of the cop only with a delay. This engenders the danger of a strong reduction of the tensile force of winding, to a certain extent "over-delivery" of the filament yarn. This can lead to winding faults in the end areas. Here, the type of winding onto the cop is important.
There are different kinds of winding, specifically flyer, cop, compound and combination winding. In flyer winding, the ring holder drive is moved back and forth with an amplitude which decreases in the course of continuing winding onto the cop, the winding therefore always takes place in the cylindrical section of the respective layer. The above explained problem of "over-delivery" in the end areas does not occur. But, flyer winding is very susceptible to dirt and damage since the complete cop is affected when a problem occurs in only a small area.
In compound winding and cop winding the situation is somewhat different. A cop which has been wound using the combination method the least sensitive. Here, the amplitude with which the ring holder drive is moved back and forth changes periodically between the full winding length of the cop and the winding length of the cylindrical middle area.
Especially in combination winding of the cop, does the above explained problem of reduction of winding tensile force arise. It is the more noticeable, the greater the difference between the diameter of the middle area of the completely wound cop and the raw diameter of the cop. Finally, for a long time this problem has limited the maximum attainable cop diameter and the cop weight.
For purposes of controlling the movement of the ring holder by the ring holder drive, especially for fixing the reversal points of the ring holder motion, fixed operating points for the ring holder drive are usually stipulated. The prior art (the previously mentioned published German Patent Application DE-A-196 07 790) discloses continually scanning the current diameter of the cop in the different areas, especially by proximity optical scanning. However, in many cases, this control engineering effort is not acceptable.